/*
 * MD5 hash implementation and interface functions
 * Copyright (c) 2003-2005, Jouni Malinen <j@w1.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 */

#include "includes.h"

#include "common.h"
#include "md5.h"
#include "crypto.h"


/**
 * hmac_md5_vector - HMAC-MD5 over data vector (RFC 2104)
 * @key: Key for HMAC operations
 * @key_len: Length of the key in bytes
 * @num_elem: Number of elements in the data vector
 * @addr: Pointers to the data areas
 * @len: Lengths of the data blocks
 * @mac: Buffer for the hash (16 bytes)
 * Returns: 0 on success, -1 on failure
 */
int hmac_md5_vector(const u8 *key, size_t key_len, size_t num_elem,
        const u8 *addr[], const size_t *len, u8 *mac)
{
    u8 k_pad[64]; /* padding - key XORd with ipad/opad */
    u8 tk[16];
    const u8 *_addr[6];
    size_t i, _len[6];

    if (num_elem > 5) {
        /*
         * Fixed limit on the number of fragments to avoid having to
         * allocate memory (which could fail).
         */
        return -1;
    }

    /* if key is longer than 64 bytes reset it to key = MD5(key) */
    if (key_len > 64) {
        if (md5_vector(1, &key, &key_len, tk))
            return -1;
        key = tk;
        key_len = 16;
    }

    /* the HMAC_MD5 transform looks like:
     *
     * MD5(K XOR opad, MD5(K XOR ipad, text))
     *
     * where K is an n byte key
     * ipad is the byte 0x36 repeated 64 times
     * opad is the byte 0x5c repeated 64 times
     * and text is the data being protected */

    /* start out by storing key in ipad */
    os_memset(k_pad, 0, sizeof(k_pad));
    os_memcpy(k_pad, key, key_len);

    /* XOR key with ipad values */
    for (i = 0; i < 64; i++)
        k_pad[i] ^= 0x36;

    /* perform inner MD5 */
    _addr[0] = k_pad;
    _len[0] = 64;
    for (i = 0; i < num_elem; i++) {
        _addr[i + 1] = addr[i];
        _len[i + 1] = len[i];
    }
    if (md5_vector(1 + num_elem, _addr, _len, mac))
        return -1;

    os_memset(k_pad, 0, sizeof(k_pad));
    os_memcpy(k_pad, key, key_len);
    /* XOR key with opad values */
    for (i = 0; i < 64; i++)
        k_pad[i] ^= 0x5c;

    /* perform outer MD5 */
    _addr[0] = k_pad;
    _len[0] = 64;
    _addr[1] = mac;
    _len[1] = MD5_MAC_LEN;
    return md5_vector(2, _addr, _len, mac);
}


/**
 * hmac_md5 - HMAC-MD5 over data buffer (RFC 2104)
 * @key: Key for HMAC operations
 * @key_len: Length of the key in bytes
 * @data: Pointers to the data area
 * @data_len: Length of the data area
 * @mac: Buffer for the hash (16 bytes)
 * Returns: 0 on success, -1 on failure
 */
int hmac_md5(const u8 *key, size_t key_len, const u8 *data, size_t data_len,
        u8 *mac)
{
    return hmac_md5_vector(key, key_len, 1, &data, &data_len, mac);
}
